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Old   March 12, 2013, 02:52
Default Condensation in a pipe
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kelvin loh
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Hello people
I would like to what are the key setup in pre-CFX to model condensation in a pipe through heat conduction out of the pipe. inlet=vapour;outlet=water. Thank you
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Old   March 12, 2013, 07:10
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From what I have read using CFD in general to estimate phase change is both:
- Very difficult
- Gives suspect results
- Not very cheap (computationally)

If you just want to see where condensation might occur you can use this technique, which is computationally cheap AND easy to setup:

Define a new expression in CFX called Antoine Tsat. http://en.wikipedia.org/wiki/Antoine_equation
You should have Tsat = (B / (A - LogP) ) - C
A, B and C depend on the fluid, and units of temperature and pressure that you are using. The values to these constants can be found in good heat transfer or thermodynamics text books.

The next step is to define a new dimensionless variable in CFX called Tstar. You can say
Tstar = ( T - Tsat ) / Tsat then you can plot Tstar in post processing see where condensation inside your pipe might occur. If Tstar > 0, condensation may not occur (since T will be greater than Tsat). If Tstar < 0 condensation may occur (since T is less than Tsat).

Using this method is just an indication and should be used with care.
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Old   April 5, 2013, 02:42
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alright thanks a lot!
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cfx & fluent, condensation., heat conduction, pipe inside pipe

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